Steam desulfurization process



STEAM DESULFURIZATION PROCESS Filed March 11, 1968 DESULFURIZED LIGHTOIL WATER PARATOR n :1 S E 8 9 o m n. 3 o o 2 Q '5 n: N E E2 h. E D 8INVENTOR. g CLYDE L. ALDRIDGE ATTORNEY United States Patent US. Cl.208-248 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to acontinuous process for the desulfurization of heavy petroleum oils inthe presence of steam and a catalyst comprising a supported metal saltin which the metal is selected from the group consisting of metals ofGroups I-A, III-B, V-B, VIB, VII-B, VIII-B, thorium and the LanthanideSeries of the Periodic Table.

This application is a continuation in part of my application Ser. No.559,932, filed June 23, 1966.

The steam desulfurization process of the invention is applied to a heavypetroleum feedstock. The three major characteristics of some heavypetroleum oils, such as residuums are that they contain (1) asphaltenesand other high molecular weight aromatic structures which severelyinhibit the rate of desulfurization, and cause catalyst deactivation,(2) ash forming constituents such as metalloorganic compounds whichcontaminate catalysts and interfere with catalyst regeneration, and (3)a relatively large quantity of sulfur which is difiicult to remove andwhich gives rise to objectionable quantities of S0 and S0 uponcombustion when it is not removed.

The most effective method for removal of sulfur from heavy oils withoutsubstantial conversion of the oil to light hydrocarbons is catalytichydrodesulfurization. Obviously the high cost of hydrogen places severeeconomic debits on this process.

For this reason, desulfurization with steam is of interest because ofthe relatively low cost of steam. The principal object of this inventionis to provide a process for the desulfurization of heavy petroleumfractions with steam in the presence of an active catalyst. The processis centered on nondestructive desulfurization as distintinguished fromdestructive desulfurization, e.g. steam cracking. Thus conversion to gasand light ends is minimized. Another object of this invention is todisclose a continuous catalytic steam desulfurization process featuringa durable, regenerable catalyst. Further objects and advantages of theinvention will be apparent from the following description whichdiscloses certain nonlimiting embodiments. The drawing is a schematicrepresentation of a preferred mode of conducting the process.

Summarizing briefly, the objects of the invention are attained bydesulfurizing heavy petroleum oils at moderate conditions in thepresence of steam and a catalyst comprising a metal salt in which themetal is selected from the group consisting of metals of Groups I-A,III-B, V-B, VIB, VII-B, VIII-B, thorium and the Lanthanide Series of thePeriodic Table, said metal salts being supported on a durable carrierwhich can be regenerated, preferably by burning.

The process feedstock is a heavy petroleum oil. The oil can be a heavyoil fraction such as atmospheric gas oil or vacuum gas oil, adeasphalted oil, whole crude oil or a residual fraction such asatmospheric distillation bottoms or vacuum distillation bottoms. Thefeed can be Patented Feb. 10, 1970 a blend of any of the oils mentionedabove as well as such refinery materials as coker distillates, catcracked fractions, visbreaker fractions, etc. One of the most suitablefeeds for the process is a petroleum fraction or a petroleum residuumcontaining at least 10 vol. percent of material boiling above 900 F. andhaving a Conradson Carbon of at least 2. The feeds will contain 0.5-l0wt. percent sulfur, 10-2000 p.p.m. metals, and they may also containnitrogen compounds. Another preferred feed is a gas oil boiling in therange of from about 400 F. to about 1000 F. The process can also beapplied to certain fractions derived from coal, oil shale and tar sands.The feed can be oxidized by contact with an oxygen containing gas tomake it more amenable to steam desulfurization. The feed can be dilutedwith a light oil.

The catalyst comprises a metal salt on a support. In the broad sense themetal is selected from the group consisting of metals of Groups IA,IIIB, V-B, VIB, VII-B, VIII-B, thorium and the Lanthanide Series of thePeriodic Table. Appropriate salt forms include the oxides, thehydroxides, the sulfides, the sulfates, the carbonates and hydrates ofthese salt forms.

Salts of certain metals are more active than others and the preferredmetals are thorium, yttrium, lanthanum, cerium, neodymium, samarium andrare earth mixtures containing several rare earths and in some casesyttrium, thorium and lanthanum. The rare earth mixtures are usuallycrude naturally occurring or semirefined mixtures.

Certain salts are more suitable to catalyst preparation and thenitrates, the oxide hydrates, the chlorides and the carbonates of thepreferred group of metals are ordinarily used.

The most preferred catalysts are hydrated mixed rare earth oxides,hydrated lanthanum oxide, and thorium oxide.

The catalyst support is an important aspect of the invention. Thesupport must be able to withstand continuous intimate contact with steamduring the desulfurization reaction and frequent contact with hot gasesduring regeneration to remove carbonaceous deposits laid down during thereaction. Suitable support materials include alumina, silica alumina,bauxite, kieselgnhr, molecular sieves, natural and synthetic zeolites,magnesia, charcoal. Alpha alumina is the most preferred support.

The catalyst should have a surface area of at least about 1.0 m. g. Thefinished catalyst can be in the form of extrudates, pills, spheres orany other attrition resistant form.

As stated in my earlier application it is believed that the in situactive catalyst form is a hydrate formed by contact with the steam.

EXAMPLE I A catalyst suitable for use in steam desulfurization wasprepared in the following manner. 7.15 gms. of lanthanum carbonate (CityChemical Company, New York, N.Y.) was dissolved in an excess of dilutenitric acid and added to 50 gms. of alpha alumina (Type SAHT- 99,Canborundum Company, Latrobe, Pa.). Suflicient Water was included tothoroughly wet the mixture. The mixture was stirred, blended and driedover night in an atmosphere of air at about C. 59 gms. of catalyst wasrecovered. The catalyst contained about 15 wt. per cent lanthanum saltsand salt hydrates and the balance alumina support.

EXAMPLE II A preferred catalyst for steam desulfurization was made in amanner similar to that set forth above except that concentrated (1/ 1)acid was used and the active ingredient was 4.34 gms. of commercialmixed rare earth oxide hydrate (Trona-American Potash and ChemicalCorporation). After compositing with the alumina sup port the catalystcontained about 1 wt. percent rare earth oxide hydrate and the balancealumina.

Referring to the drawing, an oil feed of the type previously mentionedis passed by line 1 through heat exchanger 2 to the upper section ofreactor 3. The oil is preferably heated to a temperature near thedesired temperature of the reactor. Steam enters the reactor via line 4.Air for in situ feed oxidation and/or regeneration of the catalyst isfed into the reactor via lines and 4. In this embodiment the reactantspass cocurrently down through the fixed catalyst beds. If desired thereactor can be operated with cocurrent flow of steam, air and oilupwardly through the reactor or the steam and air can be passedupwardly, countercurrent to the downwardly moving oil.

Typical steam desulfurization reaction conditions are as follows:

TABLE I.REACTION CONDITIONS, STEAM DESULFURI- ZATION In this embodimenta fixed bed of catalyst is used, however alternate means of contactingsuch as a fluidized bed, moving bed, slurry, ebbulating bed, etc. can beemployed. The catalyst is selected from those mentioned previously and apreferred catalyst is the mixed rare earth catalyst of Example 2.

Regeneration is accomplished by cutting off the flow of oil and passinga steam-air mixture from lines 4 and 5 through the catalyst bed undercombustion conditions to burn carbonaceous deposits from the catalystsurfaces. Air contents of 30( vol. percent air on steam) and bedtemperatures in the range of 500 to 2000 F. are used for regeneration.

A plurality of reactors can be operated in stages so that one or morereactors are in the regeneration stage While the others are in steamdesulfurization operation.

It is within the scope of the invention to pass oil and catalyst throughthe reactor in slurry form and to regenerate catalyst in a separateregenerator. It is also within the scope of the invention to omitregeneration and to periodically remove a portion of spent catalyst fromthe reactor and replace it with fresh catalyst.

Steam desulfurization effiuent is removed from reactor 3 by line 6. Theefiluent comprises unreacted air, steam, hydrocarbon gases, H 8,hydrocarbon vapors, desulfurized liquid oil and partially desulfurizedoil. The efiluent is passed into separator 7. In the case of a gas oilprocess feed a major amount, e.g. 50l00 percent of the desulfurizedmaterial will be in the vapor phase. It the feed is a vacuum residuum amajor amount, i.e. 50 to 100 vol. percent will be in the liquid phase.Gases and vapors are passed overhead from the separator by line 8.Liquid material is recovered from the separator by line 10. If desired,part of the oil, e.g., from 5 to vol. percent is recycled via lines 10and 1. Desulfurized product is recovered from line 9.

The gas and vapors products are passed by line 8 through heat exchanger2 and pressure reduction valve 11 into separator 12. Separator 12 isoperated at a temperature in the range of to 300 F. and a pressure inthe range of 15 to 100 p.s.i.a. Uncondensed gases are recovered by line13. Desulfurized light oil is recovered by line 14 and water isrecovered by line 15.

The process of the invention provides a means for the desulfurization ofheavy oils without the use of expensive hydrogen. Instead low cost steamis the desulfurization agent and air can be used to oxidize, e.g.,activate the feed. The catalysts employed in the process are activepromoters of the hydrolysis reaction and are durable in continuousoperations including regentration.

I claim:

1. A process for the desulfurization of a high sulfur petroleum oilcomprising continuously contacting the oil at elevated temperature withsteam in the presence of a support mixture of rare earth salts andrecovering desulfurized oil.

2. Process according to claim 1 in which the oil contains 0.5-10 weightpercent sulfur.

3. Process according to claim 1 in which the oil contains at least 10volume percent of material boiling above 900 F. and 102000 ppm. metals.

4.. Process according to claim 1 in which the oil is a gas oil.

5. Process according to claim 1 in which the oil is an atmosphericresiduum.

6. Process according to claim 1 in which the carrier is alpha alumina.

7. Process according to claim 1 in which the feed is oxidized in situwith air.

8. Process according to claim 1 in which the catalyst is periodicallyregenerated with a steam-air mixture.

9. Process according to claim 1 in which the alumina support has asurface area of at least 1.0 square meters per gram.

10. Process according to claim 1 in which said oxide is hydrated.

References Cited UNITED STATES PATENTS 3,380,915 4/1968 Mattox et al.20828 2,813,837 11/1957 Holden 252-465 2,500,146 3/1950 Fleck et al.260-668 2,697,066 12/1954 Sieg 19650 FOREIGN PATENTS 907,770 10/1962.Great Britain.

DELBERT E. GANTZ, Primary Examiner J. NELSON, Assistant Examiner US. Cl.X.R. 208-297; 252462

